1. Field of the Invention
The present invention relates to a suspension system for a vehicle. More particularly, the present invention relates to a suspension system for a vehicle that can minimize toe change when the vehicle bumps and the front wheel is to be toe-out when the vehicle turns.
2. Description of Related Art
The suspension system of a vehicle is a device disposed between the car body and the wheels and connecting the two rigid bodies, using one or a plurality of links. The suspension system mechanically appropriately controls the relative motion between the vehicle body and the wheels by carrying a vertical motion load with a chassis spring and a shock absorber and appropriately controlling high rigidity and flexibility in the other directions.
The suspension system is supposed to provide high riding comfort to passengers by effectively blocking irregular input from roads which is generated in traveling of a vehicle, and to provide convenience for driving by appropriately controlling shaking of a vehicle which is generated by non-smoothness of roads. Further, when a vehicle travels on a non-smooth road, it is required to secure safety of the vehicle in turning and braking by maintaining the vertical load on the surfaces of tires which are in contact with the ground at an appropriate level.
The suspension system according to the prior art causes over-steer when the vehicle turns at a high speed, thereby reducing steering stability, and the steering stability of the vehicle is improved by applying toe-out to the front wheel at the outside, when the vehicle turns at a high speed, in order to prevent the over-steer.
However, when the vehicle is bounced by up-down variation of the road during straight travelling, the front wheel of the vehicle is induced to toe-out and straight travelling performance is deteriorated.
Therefore, it needs to minimize variation of bump toe during straight travelling of the vehicle, and induce the front wheel to be toe-out when the vehicle rapidly turns.
FIG. 1 is a schematic rear view of a suspension system according to a conventional art. FIG. 2 is a schematic top plan view of a suspension system according to a conventional art.
As shown in FIG. 1 and FIG. 2, a conventional suspension system includes a knuckle 10 assembled to a wheel, a strut 20 assembled to an upper portion of the knuckle 10 and supporting a load of a vehicle, a lower arm 30 having one end assembling to a lower portion of the knuckle 10 and the other end assembling to a vehicle body, and a tie rod 40 having one end assembling to a rack bar and the other end assembling to the knuckle 10.
According to a conventional suspension system, when the vehicle bumps, one end of the knuckle 10 receives torque along a pivot trajectory based on an intersection line P intersecting an extension line of the lower arm 30 and an extension line perpendicular to the strut 20.
At this time, by defining a virtual arm 32 that is assembled to the knuckle 10 based on the intersection line P, one end of the knuckle 10 receives torque along a pivot trajectory by rotation of the virtual arm 32. That is, the strut 20 and the lower arm 30 can be replaced by the virtual arm 32 when the vehicle bumps.
The other end of the knuckle 10 receives torque along a pivot trajectory of the tie rod 40 assembled to the knuckle 10.
A radius of the pivot trajectory (refer to a dotted line of FIG. 1) formed by the virtual arm 32 based on the intersection line P is bigger than a radius of a pivot trajectory (refer to a one-point chain line of FIG. 1) formed by the tie rod 40.
As shown in FIG. 2, the virtual arm 32 and the tie rod 40 are positioned at a predetermined distance from each other
With reference to the FIG. 2, the virtual arm 32 is positioned in front of the tie rod 40.
Therefore, when the vehicle bumps, the front of the knuckle 10 receives torque along the up-and-down direction based on the virtual arm 32, and the rear of the knuckle 10 receives torque along the up-and-down direction based on the tie rod 40.
Since the radius of the pivot trajectory formed by the tie rod 40 is smaller than the radius of the pivot trajectory formed by the virtual arm 32, the rear of the knuckle 10 is inwardly pulled and toe-out is generated.
As described above, when the bump is generated during straight travelling, unwanted toe-out is generated. The unwanted toe-out hinders straight travel of the vehicle.
The information disclosed in this Background of the Invention section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.